coturn crash/segmentation fault on dtls

[DiStoAGe]

In stable bionic release (same on xenial), the coturn server can crah on some DTLS connections.
The problem has been fixed on the server (version 4.5.0.8 see : https://github.com/coturn/coturn/blob/master/ChangeLog) but ubuntu 18.04 (server version) use the 4.5.0.7 version.

To reproduce :

Start coturn on /etc/turnserver.conf with a TLS cert :

cert=/etc/...
pkey=/etc/...

and NOT "no-dtls", so the UDP TLS service is started.

Now you can crash it with nmap :

sudo nmap -sU -sV -p 5349 <myip-notloopback>

Now the server in the log (/var/log/turn*.log) will show :

turnserver[1222]: segfault at 7f687d230bc0 ip 00007f687b3f8f8c sp 00007f68753438e8 error 7 in libc-2.27.so[7f687b26a000+1e7000]

=> The problem is that turnserver is running with root, so potentially be a security problem ?

I tested the last master version (4.5.1.2) on github.com/coturn/coturn it doesn't has this bug.
Last problem of CVE HTTP vulnerabilty seems to be corrected too (?)

[DiStoAGe (distoage)]

Sometimes you will need to send 2 nmap requests to crash coturn on the 2nd time.

[Seth Arnold (seth-arnold)]

Thanks for taking the time to report this bug and helping to make Ubuntu better. Since the package referred to in this bug is in universe or multiverse, it is community maintained. If you are able, I suggest coordinating with upstream and posting a debdiff for this issue. When a debdiff is available, members of the security team will review it and publish the package. See the following link for more information: https://wiki.ubuntu.com/SecurityTeam/UpdateProcedures